Control system for electric generators



M10, 1939. 6. DE CROCE CONTROL SYSTEI FOR B LECTRIC GENERATORS FiledOct. 18. 1934 3 mm 1, 2 Luis a n m R -n un 3 N \N N QM & m

INVENTOR Germ era De Croc fwlfrqzsisg 6L 27) 2 Patented'Och 10, 1939coni'nor. SYSTEM FOR ELEGIBIC GENERATORS Gennero De Croce, Wilkinsburg,Pa.,

to Westinghouse Electric &

assignor Manufacturing Company, East Pittsburgh, Pa., a corporation allnia Application 0.... is, 1934, semi N6. 748,833

My invention relates, generally, to electrical control systems, and ithas particular relation to remote control systems for electricgenerators.

The object of my invention, generally stated,

is to provide a remote control system for electric generators whichshall be simple and emcient in operation and which may be readily andeconomically manufactured and installed.

The principal object of my invention is to provide for controlling theoutput capacity of an electric generator from a remote point. I

A further object of my inventionis to provide for applying positive andnegative control impulses to the load circuit of a generator forselectively controlling its output capacity.

Another object of my invention is to provide for applying positive andnegative impulses having a fixed frequency to the load circuit of agenerator for selectively controlling its output capacity, and forpreventing the passage of the control impulses through the generator.

Still another object of my invention is to provide for applyingdifferent portions of a control frequency to the load circuit of agenerator for selectively effecting changes in its output capacity.

Other objects of my invention will, in part be obvious, and in part,appear hereinafter.

My invention, accordingly, is disclosed in the embodiment hereof shownin the accompanying drawing, and comprises the features of construction,combination of elements and arrangement of parts, which will beexemplified in the construction hereinafter set forth, and the scope ofthe application of which'will be indicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention, reference may be had to the following detailed description,taken 40 in connection with the accompanying drawing, in

which:

Figure 1 illustrates diagrammatically a concrete .embodiment of .myinvention; and

Fig. 2 illustrates diagrammatically a modification of a portion of thesystem illustrated in Fig. 1.

In order to control the output capacity of an electric generator, suchas a welding generator, means are provided for selectively controllingits field flux, in order to effect corresponding changes in the outputcapacity. Such means may comprise a rheostat connected to control theflow of current through a main field winding, or a plate of magneticmaterial, which is arranged to alter the effective field flux.The'rheostat or the mov- 5 able plate-may be operated by means of amotor mechanism, or by means of a pawl and ratchet mechanism. Since theparticular type of control for the generator forms no part of thisinvention, a conventional type of control has been illustrated in thediagram.

The control mechanism is selectively operated to cliange the outputcapacity of the generator in opposite directions by means of a pair ofpolarized relays, which are inversely connected to the load circuit ofthe generator. In order 0 to selectively operate the polarized relays,the output of an alternating-current generator source is rectified andeither positive or negative half cycles are applied to the load circuit.On the application of either positive or negative half cycles 15 to theload circuit, the polarized relays may be selectively operated to effectthe desired functioning of the operating mechanism for making thedesired changes in the output capacity of the generator. 20

Since the control impulses are in the form of half waves of alternating,current, they readily pass through a capacitor which does not permitthe passage of direct current. The polarized re!- lays may, therefore,be connected through one or 25 more capacitors to the load circuit, andthey will be operated only on the application of positive or negativeimpulses, but they will not be operated on the application of directcurrent-to the load circuit. 30

It is desirable to' increase the effective impedance of the generator atthe control frequency, in order that a maximum control voltage may beapplied to the windings of the polarized relays. For this purpose, acircuit, which may be tuned ,36 to be parallel resonant at the controlfrequency,

.is connected in series circuit relation with the generator. While thetuned circuit will; readily permit the flow of welding current, itoffers substantially an open circuit effect to the control so frequencyand, therefore, it is only necessary to provide a relatively smallsource ofalternatingcurrent for effecting the desired control.

Referring now particularly to Fig. l of the drawing, the referencecharacter iii designates, 45

generally, a welding generator, which may be of any suitable type, andwhich is arranged to supply current to a load circuit which may berepresented by conductors II and II. In this instance, the generator 10is arranged to supply 50- current to a welding arc and. as is customary,the conductors II and I! are connected, respectively, to a weldingelectrode l1 and work II on which a welding operation is to beperformed.

As illustrated, the welding generator in is of so the direct-currenttype. having an armature I5 and a differential series field winding I.The

armature. l5 and field winding ii are connected in series circuitIrelation through an inductor ll to the-conductors H and ii. Theinductor I! tomary movable arm 2| engaginga resistor'22,

as illustrated.

Any suitable driving means may be .provided' for the generator Ill andexciter l9. As illustrated, an induction motor, shown generally at 23,is provided for driving both the generator l0 and'the exciter l9, whichmay be mounted on a common shaft.

With a view to remotely controlling the func tioning of the fieldrheostat in order to effect corresponding changes in the outputcapacityoi the generator ill, a mechanism is provided for selectivelyeflecting the movement of the arm 2|. As illustrated, the arm 2| ismounted on a shaft 21 on which ratchet wheels 28 and 29 are alsomounted. It will be observed that the teeth of the ratchet wheels 28 and29.

are oppositely disposed, so that when the pawls 30 and 3| respectivelyare operated, they will be moved in opposite directions.

The pawls 30 and 3| have attached thereto respectively armatures 32 andI, which are disposed in operative relation to solenoids 34 and 35. Whenthe solenoid 34 is energized, the pawl 30 is moved downwardly, and thearm II is moved in a clockwise direction to reduce the resistanceconnected in series circuit relation with the field winding II. Thefield current correspondingly increases and the output capacity of thegenerator Ill is raised. In like manner, when the pawl 3| is moveddownwardly'on energization oi the solenoid 85, the arm II is moved in acounterclockwise direction and the resistance in series circuit relationwith the main field winding I8 is increased. The field current flowingtherethrough is correspondingly decreased, and in accordancetherewlth,'the output capacity of the generator ll is decreased.

The solenoids 34 and 35 maybe selectivelyenergized by means of polarizedrelays, shown generally at 38 and 39. Each of the polarized relays 3 beenergized on the comprises contact members "it and 39a, which, asillustrated, are arranged to connect the solenoids 34 and'35 across theconductors II and I 2. It will beunderstood that any other suitablesource for energizing the solenoids l4 and '35 may be provided, but forconvenience, the conductors i I and II are employed. The polarizedrelays 38 and 39 also comprise operating winding's 38w and 3910 andrectifiers lit and 381'. The rectifiers Mr and "r may be of thecopperoxide type and, as illustrated, they are oppositely connected, sothat the energizing winding 3814; will be energized on the application'01 one polarity, while the operating winding "to will application ofanother pclarity. V

It will be observed: that two rectifiers 381' and two rectlfiers 39r areprovided and that-the common connections between each set are connected.This arrangement is provided in order to afiord a discharge path aroundeach of the operating windings 38w and 3810 which does not include theother operating winding.

In order to render the operating windings 38w and 39w non-responsivewhen direct current is applied to the load circuit represented by theconductors II and I2, a capacitor 40 is connected in series circuitrelation between the operating windings 3810 and 39w, and the loadcircuit. While a single capacitor 40 is illustrated, it will be readilyunderstood that a capacitor individual to each of the operating windings3810 and 3810 may be provided.

The control of the polarized relays 38 and 39 may be selectivelyeffected by applying to the load circuit either positive or negativeimpulses at a fixed frequency. As illustrated, a readily portablecontroller shown generally at 42, may be provided at any point. Theapparatus included in the controller 42 is indicated by the broken linesand two conductors leading thereto are illustrated. One of theseconductors, it will be readily understood, may be connected to ground orwork i4, while the other may be connected to the conductor II orelectrode I 3.

The controller 42 comprises an alternatingcurrent generator, showngenerally at 43. Since ordinarily, only direct currentwill be readilyavailable, it is desirable to use a very simple type ofalternating-current generator. This is represented by the relay 44,which comprises an operating winding 4fiu,'back contact members 44a, and44b, and front contact members 440, all of which are arranged to beengaged by a movable contact member 44m that is attracted onenergization of the operating winding 44w.

The contact members 44b and 440 are connected, as illustrated, to theterminals of a primary winding 45 of a transformer, shown generally at46. The primary winding 45 is tapped at its mid-point and is connected'to conductor H of the load circuit. As illustrated, the movable contactmember 44m is connected to the other conductor i l of the load circuit.

. 0n energization of the operating winding 44w, the lower half of theprimary winding 45- is energized, and current fiows therethrough. Atcontact members 44a, the energizing circuit for the operating winding44w is opened,'and it is imtact member 44b. It will then be understoodthat the foregoing cycle of operations is repeated rapidly at a .rate,depending upon the adjustment of the relay 44. As a result, analternating cun'ent is induced into the secondary winding 41 of thetransformer 46, which may be rectified by means of a rectifier 48,similar to the rectifiers 381' and 391', and applied to the loadcircuit.

It will-be understood that any other suitable type ofalternating-current generator may be provided, but as set forth above, agenerator of the relay type appears to be best suited i'or thisapplication. V

The iectified output oi the transformer may be applied to the loadcircuit by means or control switches 49 and 50. When the control switch49 is operated, the load circuit has applied there- I to halt waves ofone polarity, while when the relay 38 or the polarized relay 39 will beoperage which exists between the conductors II and II, a volt-meter 5|may be provided. The voltmeter 5l, while forming no part of the controlapparatus, may be provided, in order to give the operator an indicationof the voltage which exists on the load circuit, for the purpose ofgiving him a standard of comparison.

. It will be observed that the armature I! and series field winding l8of .the generator l9 provide a comparatively low impedance path betweenthe conductors I l and l! of the load circuit. In eflect, they providesuch a low impedance path around the polarized relays II and 39 that itis difiicult to provide sufiicient control current for effecting thedesired operation. It is, therefore, desirable to prevent the passage ofcontrol current-through the armature l5 and field winding It. For thispurpose, the inductor i1 is provided with a capacitor 52 connected inshunt circuit relation therewith. The inductor 11 and capacitor 52 arepreferably tuned to be parallel resonant at the frequency whichissupplied by the generator A relatively high impedance path will then beprovided between the armature l5 and field winding it of the generatorl0 and the load circuit. As a result, substantially all of the controlfrequency will be available for effecting the operation of the polarizedrelays 38 and 99.

While the inductor II, which is normally used for reducing transients inthe load circuit, has

" been illustrated as also being used in coniunc-' tion with thecapacitor 52, it will be readily understood that a separate inductor maybe used if the inductance of the inductor I1 -is not satisfactory; forthe purpose set forth.

' In describing the operation of the foregoing remote control system, itwill be assumed that the generator II and exciter i9 are being driven bythe motor 29, and that operating voltage is applied to the load circuitrepresented by the conductors II and II. It will also be assumed thatthe generator 99 is operating and that the electrode II is out of.engagement with the work M.

The circuit for energizing the operating winding 10 of the generator 43may be traced from energizing conductor ll, through conductors 55 andI6, movable contact member 1n, back contact member a, conductor 51,operating winding 10, and conductors 59 and 59 to the energizedconductor l2.

As soon, however, as the movable member m moves out of engagement withthe back contact member a, the energizing circuit for the operatingwinding w is opened and it is deenergized.

The generator 43 is so arranged that the mov' able contact member mengages the front contact member 0, so that the lower half of theprimary winding 95 is energized. On the return of the movable contactmember m, the lower half of the primary winding 49 is deenergized, andat contact member m, a circuit is completed for energizing the upperhalf of the primary winding 49.

It will be assumed that it is desired to eflect the operation of thepolarized relay 99 and to energize its operating winding "to. Thecontrol switch 49 is then depressed to complete the energizing circuit.As long as the control switch 49 is held in they operated position, theoperatin energized.

contact winding saw of the polarized relay :0 will be The circuit forenergizing the operating winding 9810 may be traced from the positiveterminal of the rectifier ll through conductors to and SI, contactmembers 49b, conductors I5 and II,

capacitor 49, rectifiers "r, operating winding 39w, conductors l2, I9,59 and 82, contact members 99a, conductors 99 and 94, and secondarywinding" to the negative terminal of the rectifier ll. If it is desiredto operate the polarized relay 99, the control switch 59' may bedepressed. .A circuit is then completed for applying half-waves to theload circuit, which are opposite in polarity to those which are appliedwhen the control switch 49 is depressed.

The circuit for energizing the operating winding 3910 may be traced fromthe positive terminal of the rectifier 48 through conductors 89 and 6|,contact members 501), conductors 59 and i2,

rectifiers 391-, operating winding 39w, capacitor Ill, conductors ll, 55and 65, contact members 50a, conductors I9 and N and secondary winding41 to the negative terminal of the rectifier 48.

At contact members 39a and 99a, obvious energiz'ing circuits for thesolenoids 94 and 35 are completed. The energization of-either of theoperating windings 99w or 9910 serves to move the rheostat 29 in eitherdirection for one step. It is necessary to eifect the successiveoperation of either of the polarized relays 39 or 39 in order to movethe rheostat 20 in successive steps.

It will be readily understood by those skilled in the art that thepolarized relays 38 and 39 may be employed to.control the operation of areversible motor mechanism which may be connected to move the arm 2| inopposite directions. In the event that such a mechanism is used, the

i arm 2| would continue to move in one or the fiers 49, rather than asingle one connected, as

illustrated in Fig. 1. However, insofar as the functioning of the systemis concerned, there will be no diflerence and, therefore, the circuitsillustrated in Fig, 2 of the drawing will not be described in detail.

. Since certain further modifications of'the in- 'vention may be madewithout departing from the .scope thereof, it is intended that allmatter contained in the above description, or shown in the accompanyingdrawing, shall be interpreted as illustrative and not in a limiting Iclaim as my invention:

l. A remote control system for an electric generator connected to supplydirect current to a load circuit, comprising, in comb nation, controlmeans operable to either increase or decrease the output of thegenerator, a source of control frequency, polarized relay meansconnected across the load circuit disposed to be selectively responsiveto the applicaton to said load circuit of positive or negative impulsesof said control frequency for selectively operating said control means,capacitor means interposed betweensaid polarized relay means and theload circuit and negative impulses for effecting the functioning of saidcontrol means.

2'. A remote control system for an electric generator comprising, incombination, a load circuit for the generator, raise means disposed toincrease the output of the generator, lower means disposed to decreasethe output of the generator, a polarized relay individual to each ofsaid means andinversely connected for energization across said loadcircuit, capacitor means interposed in series circuit relation with theoperating windings of said relays for preventing the energizationthereof on application of direct current to said load circuit, analternating-current generator, rectifying means for obtaining half wavesfrom said alternating-current generator, and switch means for connectingsaid generator to the load circuit through said rectifying means forselectively applying either positive or negative half waves to said loadcircuit fronisaid alternating-current generator for effecting theoperation of either of said polarized relays.

3. A remote control system for an electric generator connected to supplydirect currentto a load circuit comprising, in combination, a loadcircuit for the generator, control means operable to either increase ordecrease the output of the generator, a'source of control frequency,means for applying the control frequency to the load circuit, meansconnected across the load circuit responsive to the application of saidcontrol frequency to the load circuit for effecting the functioning ofsaid control means, and a filter circuit tuned to parallel resonance atsaid control frequency and connected in the load circuit'in seriescircuit relation with the generator between said generator and thefrequency responsive means for increasing the impedance of the generatorto said control frequency.

4. A remote control system for an electric generator connected tosupply-direct current to a load circuit comprising, in combination,control means operable to either increase or decrease the output of thegenerator, a source of control frequency, means forapplying differentportions of the control frequency to the load circuit, means connectedacross the load circuit and responsive to the application of differentportions of said control frequency to the load circuit for selectivelyoperating said control means, and a filter circuit tuned to parallelresonance at said control frequency and connected in the load circuitbetween the generator and the frequency responsive means for increasingthe impedance of the generator to said control frequency.

5. A remote control system for an electric generator connected to supplydirect current to a load circuit comprising, in combination, controlmeans operable to either increase or decrease the output of thegenerator, means for generating a control frequency, means forselectively applying either positive or negative half cycles of saidcontrol frequency to the load circuit, means connected to the loadcircuit responsive to the application of the positive or'. negative halfcycles of said control frequency for selectively effecting thefunctioning of said control means, and a filter circuit tuned toparallel resonance at said control frequency andconnected in the loadcircuit 6. A remote control system for an electric generator connectedto supply direct current to a load circuit comprising, in combination,control means operable to either increase or decrease the 1 output ofthe generator, means for generating a control frequency, polarized relaymeans connectedto the load circuit disposed to be responsive totheapplication to said load circuit of positive or negative impulses ofsaid control frequency for selectively operating said control means,means for selectively applying to the load circuit said impulses foreffecting the functioning of said control means, and a fllter circuittuned to parallel resonance at said frequency and connected inthe loadcircuit between the generator and the polarized relay means forincreasing the impedance of the generator to said control frequency.

'7. A remote control system for an electric generator connected tosupply direct current to a load circuit comprising, in combination,raise means disposed to increase the output of the generator, lowermeans disposed to decrease the output of the generator, a polarizedrelay individual to each of said means and inversely connected forenergization across said load circuit, capacitor means interposed inseries circuit relation with the operating windings of said relays forpreventing the energization thereof on application of direct current tothe load circuit, an alternating current source disposedto generate acontrol frequency, rectifying means for obtaining half waves from saidalternating-current source, switch means operable in conjunction -withthe rectifying means for selectively applying either positive ornegative half waves to the load circuit from said alternating-currentsource for effecting the functioning of either of said polarized relays,and a filter circuit tuned to parallel resonance at said controlfrequency and connected in the load circuit between the generator andthe polarized relays for increasing the impedance of the generator tosaid control frequency.

8. A remote control system for an electric generator comprising, incombinatiom'a load circuit for the generator, raise means disposed toincrease the output of the generator, lower means disposed to decreasethe output of the generator, a relay individual to each of said meansand disposed to control the operation thereof, an operating winding foreach of said relays, a rectifier connected in series circuit relationwith each of said windings across said load circuit, said rectifiersbeing oppositely connected to permit the energization ofone of saidwindings on application of one polarity and the energization of theother of said windings on application of another polarity, capacitormeans interposed in series circult relation with said operating windingsto prevent the energization thereof on application of direct current tosaid load circuit, an alternating- I current generator, rectifying meansfor obtaining half waves from said generator, and switch means operablein conjunction with the rectifiers for selectively applying eitherpositive or negative half waves to said load circuit from saidalternating-current generator for effecting the energization of eitherof said operating windings.

9. A remote control system comprising, in combination, a direct-currentgenerator, a load circuit for the generator, field varying means forthe, 7s

generator, motor means operatively connected to said field varyingmeans, a control frequency generator, circuit means including controlswitch means for connecting the control frequency generator .to the loadcircuit to selectively apply thereto a control frequency ofpoeitive ornegative impulses, and frequency responsive means connected to said loadcircuit and selectively responsive to said positive and negativeimpulses disposed to initiate the operation of said motor means onapplication of control frequency to said load circuit to change theoutput of said generator.

10. A remote control system comprising, in combination, a direct-currentgenerator, a load circuit for said generator, a main field winding insaid generator, a rheostat connected to vary the flow of excitingcurrent through said main fleld winding, motor means having drivingconnection with said rheostat for operating it, a source of controlfrequency circuit means including rectiiier means for connecting thesource of control increase or decrease frequency to said load circuit toselectively apply thereto a control frequency of positive or negative,half waves, and frequency responsive means connected to said loadcircuit and selectively re- .sponsive to the control frequency disposedto initiate the functioning of said motor means on application ofcontrol frequency to said load circuit to change the output of saidgenerator.

11. A remote control system for a direct cur-- rent generator,comprising, a load circuit for the generator, control means operable toeither the output of the generator, a source of control frequency,rectifier means, manually operable means for connecting the source ofcontrol frequency to the load circuit through said rectifier means toselectively apply thereto a frequency of either positive or negativepolarity, and relay means connected across the load circuit selectivelyresponsive to the positive and negative frequencies applied thereto forselectivelyoperating said control means.

GENNERO DE CROCE.

